Supported Tetrahedral Oxo-Sn Catalyst: Single Site, Two Modes of Catalysis.

Mild calcination in ozone of a (POSS)-Sn-(POSS) complex grafted on silica generated a heterogenized catalyst that mostly retained the tetrahedral coordination of its homogeneous precursor, as evidenced by spectroscopic characterizations using EXAFS, NMR, UV-vis, and DRIFT. The Sn centers are accessible and uniform and can be quantified by stoichiometric pyridine poisoning. This Sn-catalyst is active in hydride transfer reactions as a typical solid Lewis acid. However, the Sn centers can also create Brønsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the neighboring Sn-O-Si bond. The resulting acidic silanol is active in epoxide ring opening and acetalization reactions.

The effect of Mg location on Co-Mg-Ru/γ-Al2O3 Fischer-Tropsch catalysts.

The effectiveness of Mg as a promoter of Co-Ru/γ-Al2O3 Fischer-Tropsch catalysts depends on how and when the Mg is added. When the Mg is impregnated into the support before the Co and Ru addition, some Mg is incorporated into the support in the form of MgxAl2O3+x if the material is calcined at 550°C or 800°C after the impregnation, while the remainder is present as amorphous MgO/MgCO3 phases. After subsequent Co-Ru impregnation MgxCo3-xO4 is formed which decomposes on reduction, leading to Co(0) particles intimately mixed with Mg, as shown by high-resolution transmission electron microscopy. The process of impregnating Co into an Mg-modified support results in dissolution of the amorphous Mg, and it is this Mg which is then incorporated into MgxCo3-xO4. Acid washing or higher temperature calcination after Mg impregnation can remove most of this amorphous Mg, resulting in lower values of x in MgxCo3-xO4. Catalytic testing of these materials reveals that Mg incorporation into the Co oxide phase is severely detrimental to the site-time yield, while Mg incorporation into the support may provide some enhancement of activity at high temperature.

Graphite-Conjugated Rhenium Catalysts for Carbon Dioxide Reduction.

Condensation of fac-Re(5,6-diamino-1,10-phenanthroline)(CO)3Cl to o-quinone edge defects on graphitic carbon surfaces generates graphite-conjugated rhenium (GCC-Re) catalysts that are highly active for CO2 reduction to CO in acetonitrile electrolyte. X-ray photoelectron and X-ray absorption spectroscopies establish the formation of surface-bound Re centers with well-defined coordination environments. GCC-Re species on glassy carbon surfaces display catalytic currents greater than 50 mA cm(-2) with 96 ± 3% Faradaic efficiency for CO production. Normalized for the number of Re active sites, GCC-Re catalysts exhibit higher turnover frequencies than that of a soluble molecular analogue, fac-Re(1,10-phenanthroline)(CO)3Cl, and turnover numbers greater than 12,000. In contrast to the molecular analogue, GCC-Re surfaces display a Tafel slope of 150 mV/decade, indicative of a catalytic mechanism involving rate-limiting one-electron transfer. This work establishes graphite-conjugation as a powerful strategy for generating well-defined, tunable, heterogeneous electrocatalysts on ubiquitous graphitic carbon surfaces.

Single-Site Organozirconium Catalyst Embedded in a Metal-Organic Framework.

A structurally well-defined mesoporous Hf-based metal-organic framework (Hf-NU-1000) is employed as a well-defined scaffold for a highly electrophilic single-site d(0) Zr-benzyl catalytic center. This new material Hf-NU-1000-ZrBn is fully characterized by a variety of spectroscopic techniques and DFT computation. Hf-NU-1000-ZrBn is found to be a promising single-component catalyst (i.e., not requiring a catalyst/activator) for ethylene and stereoregular 1-hexene polymerization.

A Hafnium-Based Metal-Organic Framework as a Nature-Inspired Tandem Reaction Catalyst.

Tandem catalytic systems, often inspired by biological systems, offer many advantages in the formation of highly functionalized small molecules. Herein, a new metal-organic framework (MOF) with porphyrinic struts and Hf6 nodes is reported. This MOF demonstrates catalytic efficacy in the tandem oxidation and functionalization of styrene utilizing molecular oxygen as a terminal oxidant. The product, a protected 1,2-aminoalcohol, is formed selectively and with high efficiency using this recyclable heterogeneous catalyst. Significantly, the unusual regioselective transformation occurs only when an Fe-decorated Hf6 node and the Fe-porphyrin strut work in concert. This report is an example of concurrent orthogonal tandem catalysis.

A retrospective analysis of dentofacial deformities and orthognathic surgeries using the index of orthognathic functional treatment need (IOFTN).

OBJECTIVES: To assess the functional needs of orthognathic cases treated in Northampton General Hospital using the index of orthognathic functional treatment need (IOFTN). MATERIALS AND METHODS: A retrospective study was conducted on 78 subjects (54 female and 24 males, 10-54 years, mean (SD) age=21.88 (6.98) years) who had orthognatic surgery in Northampton General Hospital or were in preparation for it (5 case). The sample represents a period between February 1997 and December 2014. The components of IOFTN and Dental Health Component (DHC) of the Index of Orthodontic Treatment Need (IOTN) as well as Malocclusion type were recorded. RESULTS: Class III malocclusion/skeletal pattern was the most prevalent type (approximately 49%). There were 1, 36, 3, and 38 subjects with Class I, Class II Division I, Class II Division II, and Class III malocclusions, respectively. In terms of sagittal skeletal relationship, there were 2, 37, and 39 subjects with Class I, Class II, and Class III skeletal bases, respectively. The most prevalent IOFTN score in our sample was the 5.2 (29.5%), followed by 5.3 (15.5%), 4.2 (13%), 4.3 (11.5%). Overall, 92.3% were classified as in great and very great functional needs according to the IOFTN. Similarly, 84.6% scored as grade 4 or 5, according to the IOTN (DHC). The bimaxillary type osteotomy was the most prevalent type (61.5%). CONCLUSIONS: Using IOFTN, 92.3% of our sample were classified as having great and very great functional needs. IOFTN is a simple and reliable tool to identify patients in need of orthognathic surgery and can be used in resource allocation for patients with highest functional needs.

Benzene selectivity in competitive arene hydrogenation: effects of single-site catalyst···acidic oxide surface binding geometry.

Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ≫ AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.

Structural evolution of an intermetallic Pd-Zn catalyst selective for propane dehydrogenation.

We report the structural evolution of Pd-Zn alloys in a 3.6% Pd-12% Zn/Al2O3 catalyst which is selective for propane dehydrogenation. High signal-to-noise, in situ synchrotron X-ray diffraction (XRD) was used quantitatively, in addition to in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) and extended X-ray absorption fine structure (EXAFS) to follow the structural changes in the catalyst as a function of reduction temperature. XRD in conjunction with DRIFTS of adsorbed CO indicated that the ß1-PdZn intermetallic alloy structure formed at reduction temperatures as low as 230 °C, likely first at the surface, but did not form extensively throughout the bulk until 500 °C which was supported by in situ EXAFS. DRIFTS results suggested there was little change in the surfaces of the nanoparticles above 325 °C. The intermetallic alloy which formed was Pd-rich at all temperatures but became less Pd-rich with increasing reduction temperature as more Zn incorporated into the structure. In addition to the ß1-PdZn alloy, a solid solution phase with face-center cubic structure (α-PdZn) was present in the catalyst, also becoming more Zn-rich with increasing reduction temperature.

Air- and water-resistant noble metal coated ferromagnetic cobalt nanorods.

Cobalt nanorods possess ideal magnetic properties for applications requiring magnetically hard nanoparticles. However, their exploitation is undermined by their sensitivity toward oxygen and water, which deteriorates their magnetic properties. The development of a continuous metal shell inert to oxidation could render them stable, opening perspectives not only for already identified applications but also for uses in which contact with air and/or aqueous media is inevitable. However, the direct growth of a conformal noble metal shell on magnetic metals is a challenge. Here, we show that prior treatment of Co nanorods with a tin coordination compound is the crucial step that enables the subsequent growth of a continuous noble metal shell on their surface, rendering them air- and water-resistant, while conserving the monocrystallity, metallicity and the magnetic properties of the Co core. Thus, the as-synthesized core-shell ferromagnetic nanorods combine high magnetization and strong uniaxial magnetic anisotropy, even after exposure to air and water, and hold promise for successful implementation in in vitro biodiagnostics requiring probes of high magnetization and anisotropic shape.

Proxy-based accelerated discovery of Fischer-Tropsch catalysts.

Development of heterogeneous catalysts for complex reactions such as Fischer-Tropsch synthesis of fuels is hampered by difficult reaction conditions, slow characterisation techniques such as chemisorption and temperature-programmed reduction and the need for long term stability. High-throughput (HT) methods may help, but their use has until now focused on bespoke micro-reactors for direct measurements of activity and selectivity. These are specific to individual reactions and do not provide more fundamental information on the materials. Here we report using simpler HT characterisation techniques (XRD and TGA) along with ageing under Fischer-Tropsch reaction conditions to provide information analogous to metal surface area, degree of reduction and thousands of hours of stability testing time for hundreds of samples per month. The use of this method allowed the identification of a series of highly stable, high surface area catalysts promoted by Mg and Ru. In an advance over traditional multichannel HT reactors, the chemical and structural information we obtain on the materials allows us to identify the structural effects of the promoters and their effects on the modes of deactivation observed.

Tetrahedral Sn-silsesquioxane: synthesis, characterization and catalysis.

A tetrahedral stannasilsesquioxane complex was synthesized as a racemic mixture using Sn(O(i)Pr)4 and silsesquioxanediol, and its structure was confirmed with X-ray crystallography, NMR, and EXAFS. The complex was a Lewis acid, and both anti and syn-binding with Lewis bases were possible with the formation of octahedral Sn complexes. It was also a Lewis acid catalyst active for epoxide ring opening and hydride transfer.

Assignment of the oxidation states of Zr and Co in a highly reactive heterobimetallic Zr/Co complex using X-ray absorption spectroscopy (XANES).

The reduced heterobimetallic complex (THF)Zr(MesNP(i)Pr2)3CoN2 (1) has been examined along with a series of structurally similar reference compounds using X-ray absorption near edge structure (XANES) spectroscopy. Complex 1 has been shown to be highly reactive, often via one-electron pathways that might be expected for a d(1) Zr(III) complex. However, the presence of two strongly interacting metals in complex 1 renders the assignment of oxidation states ambiguous. Both Zr and Co K-edge XANES spectra reveal that the most accurate description of complex 1 is that of a Zr(IV)/Co(-I) zwitterion. Electronic structure calculations support this assignment.

Odontogenic cervico-fascial infections: a continuing threat.

STATEMENT OF THE PROBLEM: Dental abscesses are common and occasionally can progress to life-threatening cervico-fascial infections. Despite medical advances, odontogenic cervico-fascial infections (OCFIs) continue to be a threat. The potential seriousness of odontogenic infections (Ols), or dental abscesses, is frequently underestimated. General dental practitioners (GDPs) in primary care face the challenging decision of whether to refer patients to secondary care or to manage them in the community. PURPOSE OF THE REVIEW: This paper reviews the relevant aspects of Ols that might be helpful to primary care dental practitioners in providing a better understanding of the anatomy and pathology and aims to assist in clinical decision. METHOD: An up-to-date review of literature on OCFIs, highlighting their potential risks with clinical examples. RESULTS AND CONCLUSION: Dental abscesses are common and continue to be a major cause for emergency hospital admission to oral and maxillofacial surgery departments. They occasionally spread to fascial spaces of the neck, potentially posing significant morbidity and mortality. GDPs are usually the first point of contact and face the challenge of recognising those at risk of developing OCFIs, which are potentially life threatening and require urgent referral for hospital treatment. We propose a patient care pathway to be used in primary care.

Identification and overexpression of human neutrophil alpha-defensins (human neutrophil peptides 1, 2 and 3) in squamous cell carcinomas of the human tongue.

To date, little attention has been paid to the possible role of alpha-defensins (human neutrophil peptides 1-3), HNP-1, HNP-2 and HNP-3 in innate host defence against tumour invasion. In the current study, using a single-dimensional high pressure liquid chromatography (HPLC) method for peptide separation, followed by mass spectrometry and amino acid sequencing for identification and quantitation, we report the overexpression of HNP-1, HNP-2 and HNP-3 in squamous cell carcinomas of the human tongue compared with autogenous non-tumour tissue. Using a specific antibody we show that the defensins are abundant in neutrophils infiltrating human oral squamous cell carcinoma tissue. In the context of their previously reported oncolytic activity, our results may imply a role for alpha-defensins in host defence against oral squamous cell carcinoma.